This invention relates to a clutch engagement detecting apparatus for detecting the state of engagement of a clutch, and a single-shaft combined plant having it.
A single-shaft combined plant, having a gas turbine and a steam turbine connected by a single shaft, is a plant with a high efficiency, involving minimal emission of hazardous substances (NOX, etc.), and flexibly accommodating diurnal changes in electric power consumption. Recently, demand has grown for a further decrease in the construction cost for this single-shaft combined plant. A conventional single-shaft combined plant involved the following factors behind the cost increase:
(1) Since the gas turbine and the steam turbine are simultaneously started, there is need for a thyristor (starter) capable of generating a huge starting torque.
(2) Since the steam turbine also rotates, together with the gas turbine, at the time of starting, cooling steam needs to be supplied to the steam turbine so that the blades of the steam turbine do not excessively rise in temperature because of windage loss. However, before the generator output by the gas turbine increases, an exhaust gas boiler, which produces steam from the exhaust gas from the gas turbine, cannot form steam that can be charged into the steam turbine. Thus, until the exhaust gas boiler forms steam which can be charged into the steam turbine, there arises the necessity for an auxiliary boiler with a very high capacity enough to supply the steam turbine with sufficient cooling steam.
To reduce the construction cost, a proposal has now been made for a single-shaft combined plant to which a clutch, as shown in FIG. 10, has been applied. In FIG. 10, a gas turbine 1 and a steam turbine 2 are connected by a single shaft 3, and a generator 4 is also connected to the shaft 3. A clutch 5 is interposed between the gas turbine 1 (generator 4) and the steam turbine 2, and this clutch 5 enables the gas turbine 1 and the steam turbine 2 to be connected and disconnected. Fuel is supplied to the gas turbine 1 via a fuel control valve 7, while steam from an exhaust gas boiler or the like is supplied to the steam turbine 6 via a steam governing valve 6.
With this single-shaft combined plant using the clutch 5, only the gas turbine 1 and the generator 4 are started first, with the gas turbine 1 and the steam turbine 2 being disconnected from each other by the clutch 5. When the gas turbine 1 reaches a rated rotational speed, the generator 4 is connected to a power system. After connection of the generator to the power system, steam, which is generated by an exhaust gas boiler (not shown) with the use of an exhaust gas from the gas turbine 1, is supplied to the steam turbine 2 at a time when the steam becomes suppliable to the steam turbine 2, thereby starting the steam turbine 2. After the steam turbine 2 reaches a rated rotational speed, the clutch 5 is engaged to convey the torque of the steam turbine 2 to the generator 4.
The clutch 5 uses a helical spline engagement structure (the same as a clutch 15 shown in FIG. 6; details will be offered later). When the rotational speed of the steam turbine 2 increases to reach the same rotational speed as the rotational speed of the gas turbine, its pawl is engaged. When the rotational speed of the steam turbine 2 further increases to exceed the rotational speed of the gas turbine 1 slightly, a sliding component slides, resulting in complete engagement of a helical spline engagement portion and a main gear portion.
According to the single-shaft combined plant using the clutch 5, only the gas turbine 1 and the generator 4 are started first, so that the capacity of the thyristor necessary for starting can be decreased (the capacity may be decreased by an amount corresponding to the weight of the steam turbine 2). Moreover, during a period for which only the gas turbine 1 and the generator 4 are operated, the steam turbine 2 rotates at a low speed, requiring no cooling steam. Thus, the capacity of the auxiliary boiler can be decreased.
To satisfactorily control the above-described single-shaft combined plant using the clutch 5, there is need for a function which can accurately determine whether the clutch 5 is in an engaged state or a disengaged state.
However, whether the clutch 5 is in an engaged state or a disengaged state cannot be determined with high reliability by use of a limit switch, because when engagement or disengagement of the clutch 5 is performed, the clutch 5 itself also rotates at a high rotational speed of 3,000 rpm (50 Hz) or 3,600 rpm (60 Hz). Currently, therefore, the engagement or disengagement of the clutch 5 is detected by detecting the axial position of the sliding component of the clutch 5 with the use of a position sensor provided near the outer periphery of the sliding component without contacting the outer periphery, although a relevant construction is not shown. This position sensor is constituted such that a high frequency current is flowed through a coil at the front end of the sensor to generate eddy currents in an object of detection (the aforementioned sliding component), and changes in the impedance of the coil in response to changes in the eddy currents are measured to detect the position of the object of detection.
With this method, however, the turbines 1 and 2 themselves rotate at high speeds, oscillate vertically or laterally, and stretch or contract. On the other hand, the location where the position sensor is attached is fixed. Hence, there are limitations to accurately determining the engagement/disengagement of the clutch 5.
Therefore, the present invention has been made in view of the above circumstances. Its problem is to provide a clutch engagement detecting apparatus, which can accurately detect the state of engagement of a clutch using a helical spline engagement structure, and a single-shaft combined plant equipped with the clutch engagement detecting apparatus.
A clutch engagement detecting apparatus of a first invention for solving the above problem is a clutch engagement detecting apparatus for detecting the state of engagement of a clutch using a helical spline engagement structure interposed between a first rotating machine and a second rotating machine, characterized by having a clutch engagement determination logic which determines that the clutch is engaged if the difference between the detected value of the rotational speed of the first rotating machine and the detected value of the rotational speed of the second rotating machine is not more than the detection error of rotation detecting meters for detecting the rotational speeds of the first rotating machine and the second rotating machine at a time when a predetermined time has passed during engagement of the clutch for connecting the second rotating machine to the first rotating machine.
Thus, according to the clutch engagement detecting apparatus of the first invention, the engagement of the clutch can be detected more reliably by the clutch engagement determination logic.
A clutch engagement detecting apparatus of a second invention is the clutch engagement detecting apparatus of the first invention, characterized by having a clutch abnormality determination logic which determines that the clutch is abnormal if the detected value of the rotational speed of the second rotating machine exceeds the detected value of the rotational speed of the first rotating machine by a predetermined rotational speed or more, or if the detected value of the rotational speed of the second rotating machine falls short of the detected value of the rotational speed of the first rotating machine by a predetermined rotational speed or more after the clutch engagement determination logic has determined that the clutch is engaged.
Thus, according to the clutch engagement detecting apparatus of the second invention, an abnormality of the clutch can be detected reliably by the clutch abnormality determination logic.
A clutch engagement detecting apparatus of a third invention is a clutch engagement detecting apparatus for detecting the state of engagement of a clutch using a helical spline engagement structure interposed between a first rotating machine and a second rotating machine, characterized by including pulse generation means for outputting pulse signals at constant rotation angles of the first rotating machine and the second rotating machine, and a first counter and a second counter, and characterized in that when the clutch is engaged to connect the second rotating machine to the first rotating machine, the first counter counts the number of pulses generated from the pulse generation means in response to the rotations of the second rotating machine for a constant number of pulses generated from the pulse generation means in response to the rotations of the first rotating machine, whereas the second counter does addition or subtraction according to the counted value of the first counter, and a logic is further provided for determining the state of engagement of the clutch based on the counted value of the second counter corresponding to the relative rotation angle between the first rotating machine and the second rotating machine.
Thus, according to the clutch engagement detecting apparatus of the third invention, the engaged state of the clutch can be determined reliably. Furthermore, the engaged state of the clutch can be grasped more concretely. In detail, even when the first rotating machine and the second rotating machine rotate at the same rotational speed, this does not necessarily mean that the clutch is completely engaged. According to the third invention, by contrast, it is possible to determine whether the clutch is completely engaged, or bonded halfway through engagement.
A single-shaft combined plant of a fourth invention is a single-shaft combined plant comprising a gas turbine and a steam turbine connected together by a single shaft, and a clutch using a helical spline engagement structure interposed between the gas turbine and the steam turbine, whereby the gas turbine and the steam turbine can be connected to or disconnected from each other, characterized by including the clutch engagement detecting apparatus of the first, second or third invention, and characterized in that the first rotating machine is a gas turbine and the second rotating machine is a steam turbine.
Thus, according to the single-shaft combined plant of the fourth invention, detection of engagement of the clutch essential to the single-shaft combined plant using the clutch can be performed reliably by the clutch engagement detecting apparatus. Consequently, a single-shaft combined plant can be produced at a lower cost than in the earlier technologies, by use of the clutch.